Cell Signalling and Transduction
In the signal transduction mechanism known as protein phosphorylation

phosphorylated proteins act with enzymes to trigger the signal cascade
receptor kinases play a key role in triggering the signal cascade
the signaling molecule binds to a surface receptor
All of these

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Cell Signalling and Transduction
In terms of cell communication, what do bacterial pathogens such as cholera and anthrax have in common?

They block the normal functioning of signal transduction mechanisms
They alter the chemical structure of key signaling molecules
They prevent the production of key signaling molecules
They destroy the receptors for key signaling molecules

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Cell Signalling and Transduction
The binding of ligands to many G-proteins linked receptors leads to shortlived

decrease in the concentration of certain extracellular signaling molecules called first messenger
increase in the concentration of certain extracellular signaling molecules called first messenger
decrease in the concentration of certain intracellular signaling molecules called second messenger
increase in the concentration of certain intracellular signaling molecules called second messenger

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Cell Signalling and Transduction
Two key organizing principles for large multicellular organisms are

prokaryotic cell structure and cell specialization
communication between cells and simple nerve reflexes
simple nerve reflexes and cell specialization
cell specialization and communication between cells

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

never enter the blood of humans
bind to cell surface receptors to trigger chemical cascades
are made in one location of the body but have their effects some distance away
are hydrophilic and so cannot penetrate the plasma membrane

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